The present invention relates to manchester encoders and more particularly to a high speed manchester encoder which employs a multiplexing technique to generate the manchester code. Prior known means of generating the manchester code is by the exclusive-or logic function. The clock and data bit are applied to the inputs of an exclusive OR gate. When both inputs are 0 the output is 0. When the clock input is 0 and the data bit is 1 the output is a 1. When the clock input is 1 and the data input is 0 the output is 1. When both clock and data bit inputs are 1s the output is a 0. Space or "0" is an up transition during the bit period. Mark "1" is a down transition during the bit period. This type of manchester encoder suffers from the disadvantages of the necessity of having the trailing and leading edges of the clock and data bit in coincidence and the clock must be synchronized with the data bit.